The present disclosure relates to a semiconductor device. For example, the present disclosure relates to a semiconductor device suitable for receiving digital and analog signals accurately in a state where high general versatility is maintained.
Semiconductor systems such as a microcontroller mounted on a vehicle are required to receive not only digital signals, but also analog signals, depending on specifications. Semiconductor systems are also required to reduce the number of external terminals (pads) to thereby suppress an increase in circuit size. In addition, there is a demand for a microcomputer with high general versatility that can be used for a large number of applications without increasing the circuit size and the number of terminals.
Accordingly, in recent years, a semiconductor system incorporating an input circuit capable of selectively receiving digital and analog signals (digital/analog input circuit) has been developed. In the semiconductor system incorporating the digital/analog input circuit, pads are shared by the digital and analog signals. Accordingly, the number of pads is reduced, resulting in suppression of increase in circuit size.
However, in a semiconductor system incorporating a plurality of digital/analog input circuits that are driven by a common power supply, an edge of a digital signal input to a certain digital/analog input circuit is transmitted as noise to an analog signal input to another digital/analog input circuit via the common power supply. This causes a problem that the analog signal cannot be received accurately.
A solution to the above-mentioned problem is disclosed in Japanese Unexamined Patent Application Publication No. 2012-29155.
A semiconductor integrated circuit disclosed in Japanese Unexamined Patent Application Publication No. 2012-29155 includes resistor elements which have a resistance value depending on the type of a digital signal (a digital output signal or a digital input signal) and are disposed on an analog signal line that connects input terminals (pads), which are shared by digital and analog signals, to an AD converter that performs AD conversion of analog signals. With this configuration, the semiconductor integrated circuit reduces the effect of noise transmitted from the digital signal to the analog signal.